Method for manufacturing an insulated coil

ABSTRACT

A method for manufacturing an insulated coil comprising the steps of winding an insulating tape layer by layer around a conductor with string-like substances mainly consisting of synthetic resin inserted between the layers of the insulating tape to form a gap therearound, impregnating a synthetic resin between the layers and in the gap, and heating to fuse the synthetic resin of the string-like substance into the impregnated synthetic resin.

United States Patent [191 Takechi et al.

[ Feb. 18, 1975 l l METHOD FOR MANUFACTURING AN INSULATED COIL {75] Inventors: Taichi Takechi; Ryozi Kumazawa;

Kimikazu Umemoto; Toshimitsu Yamada; Junichi Kamiuchi, all of Yokohama; Eiji Koyanagi, Fujisawa, all of Japan [731 Assignees: Tokyo Shibaura Electric Co., Ltd.,

Saiwai-ku; Tokyo Shibaura Electric Co., Ltd., Kawasaki shi, both of, Japan [22] Filed: Dec. 13, 1973 [2]] Appl. No.: 424,273

[30] Foreign Application Priority Data Dec. 25. 1972 Japan 47-129310 [52] US. Cl 29/605, 156/56, 174/120 C, 174/120 SR, 310/208, 336/209 [51} Int. Cl. H0lf 7/06 [58] Field of Search 29/605, 602, 596;

174/120 R, 120 C, 120 SR, 121 R, 121 SR; 336/209; 310/208; 156/53, 56

[56] References Cited UNITED STATES PATENTS 2,656,290 10/1953 Bcrberich ct al. 29/605 X 3,470,045 9/1969 Bronnvall ct alt [56/53 3,531,751 9/1970 Sargent 29/605 X 3,556,925 l/l97l Mertens 1. 174/120 C X Primary Examiner-Carl E. Hall Attorney, Agent, or Firm-Oblon, Fisher, Spivak, McCelland & Maier [57] ABSTRACT A method for manufacturing an insulated coil comprising the steps of winding an insulating tape layer by layer around a conductor with string-like substances mainly consisting of synthetic resin inserted between the layers of the insulating tape to form a gap therearound, impregnating a synthetic resin between the layers and in the gap, and heating to fuse the synthetic resin of the string-like substance into the impregnated synthetic resin.

8 Claims, 9 Drawing Figures PATENTEU 3,866.316

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b s F O O O O O O O O O O O O O O O O O O 6 5 4 3 2 .1 E3 525653 QFEmoEQHm 1o IMPREGNATING PRESSURE TIME (hr) METHOD FOR MANUFACTURING AN INSULATED COIL This invention relates to a method for manufacturing an insulated coil by winding an electrically insulating tape, layer by layer, around a conductor or conductors and impregnating synthetic resin between the layers of the insulated tape.

As a method for manufacturing an insulated coil for high voltage, a vacuum/pressure impregnating method is known. This method comprises winding around a wire coil. layer by layer, an insulating tape, for example, a mica tape, including little or some synthetic resin and, after vacuum treating, pressing synthetic resin to cause it to be impregnated between the layers of the mica tape, and shaping and curing it under pressure. According to this method, when lesser turns ofthe tape are involved, synthetic resin is well impregnated between the layers of the tape and it is possible to obtain an insulated coil for relatively high voltage. However, where the turns of the insulating tape are increased in an attempt to obtain an insulating coil for even higher voltages, synthetic resin is not sufficiently impregnated between the layers of the tape and it is impossible to obtain an insulated coil for high voltage.

According to the conventional method the degree of impregnation of synthetic resin between the layers of the tape is varied by the extent to which the insulated tape is tightly wound, resulting in a poor yield with variation in quality.

It is accordingly the object of this invention to provide a method of easily manufacturing an insulated coil suitable for use with a high voltage, with little variation in quality and a high yield.

This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram schematically showing the steps as involved in manufacturing an insulated coil according to this invention;

FIG. 2 is a schematic view explaining a method for manufacturing a string-like substance as used in this invention;

FIG. 3 is a cross-sectional view of the string-like substance;

FIG. 4 is a schematic view explaining the step of winding an insulating tape around a conductor according to this invention,

FIG. 5 is a cross-sectional view as taken along line 5--5 of FIG. 4;

FIG. 6 is a cross-sectional view schematically showing the state as taken after the tape has been wounded around a conductor;

FIG. 7 is a cross-sectional view similar to FIG. 6 as taken after a heating treatment has been effected;

FIG. 8 is a graphical representation showing a comparison in electrical properties between an insulated coil manufactured according to this invention and an insulated coil manufactured according to the conventional method; and

FIG. 9 is a schematic view explaining the step of winding an insulating tape around a conductor with a string-like substance inserted between the layers of the tape.

There will be explained the method for manufacturing an insulated coil according to this invention.

An insulating tape is wound layer by layer on a conductor with a string-like substance interposed between the coiled layers of the insulating tape to leave a gap nearby (A, FIG. 1). The coiled conductor is heated at such a temperature that the string-like substance is not fused, while being vacuum treated to evacuate a gap between the coiled layers of the insulating tape and a gap created by the string-like substance (B, FIG. I). This process is effected to permit synthetic resin to be easily impregnated into these gaps during a synthetic resin impregnating process to be later described. This process of B, FIG. I is not essential to the invention. The so vacuum treated coil is impregnated with synthetic resin at a synthetic resin impregnating step (C, FIG. 1) so that synthetic resin is impregnated into the above-mentioned gaps. The impregnating process is achieved by introducing a synthetic resin into the coil wound with the insulating tape and applying a predetermined pressure. Then, the impregnated coil is heated to cause the string-like substance to be fused to permit it to be mixed with the impregnated synthetic resin, thereby presenting a shaped coil (D, FIG. 1). The string-like substance may be made entirely of synthetic resin or may be made by coating with synthetic resin a core material such as a glass fiber yarn or natural fiber yarn. Synthetic resin for the string-like substance may be made of a high-molecular-weight solids epoxy resin (commercially available under the trade name of Epikote 1,004, 1,007 etc Shell Chemical Co., Ltd. of bisphenol epichlorohydrines having an epoxy equivalent of 800 to 2,100. The inserting position, inserting state of the string-like substance and the number of string-like substances may be optionally selected. For example, one or several string-like substances may be located between the respective coiled layers of the tape or may be located at a predetermined position between the coiled layers of the tape. Where a curing agent is introduced in the impregnating synthetic resin, a curing agent may not necessarily be included in the string-like substance. The insulating tape may be preliminarily, or to a lesser extent, included with synthetic resin. For the object of this invention there may be used such a type of insulating tape as is well known in this field. For example, a mica tape, glass tape, synthetic resin tape may be normally adopted.

Explanation will now be made of the method for manufacturing an insulated coil by reference to the accompanying drawings.

A stringlike substance using as a primary component synthetic resin used in this invention is manufactured as shown in FIG. 2. That is, the above-mentioned Epikote having a melting point of about C is heated at 180 to 250C at a heating bath 10 to cause it to be molten. Through the molten synthetic resin bath a core yarn 12 of the order of denier which is made of glass or synthetic resin fiber is passed to cause synthetic resin to be coated around the core yarn. Then, the core yarn coated with synthetic resin 11 is passed through a die 13 having a suitable diameter and it is cooled and dried into a string-like substance 14 having a diameter of about 0.3 to 0.6 mm. The string-like substance consists of the core yarn 12 and an outer layer 11 coated with synthetic resin. In FIG. 2 reference numeral 15 indicates guide rolls for guiding the core yarn 12 from a bobbin 16 into a molten bath and then to a take-up roll 18, and 17 indicates a guide.

When a coil half turn is manufactured using the string-like substance 14, a core conductor 20 bent to form a half turn as shown in FIG. 4 is prepared. The core conductor is plurally wound with a mica tape 21 of 0.18 mm in thickness to obtain a 20-layered insulated coil. During the winding of the tape the string-like substances 14 are sequentially inserted two on each side of the core conductor and between the respective layers of the insulator 21. As a result, gaps are created as shown in FIG. 6 (only two gaps are shown) between the layers of the tape. The resultant coil is heated at 80C for 10 hours under vacuum of 0.5 mm Hg for drying and gaps between the tape layers are evacuated. The so vacuum treated coil is introduced into impregnating resin having a viscosity of 5 poises and then pressed for about hours to permit synthetic resin to be impregnated into the above-mentioned gap of the insulating tape. Then, the coil is heated at about 150 to 160C to cause synthetic resin constituting the string-like substance to be fused together with synthetic resin impregnated into the gap of the insulating tape, thereby presenting an integral form. Then, the coil is press-formed into a final shape.

According to the method as mentioned above, a mica tape is wound layer by layer around the conductor with string-like substances inserted between the respective layers of the insulating tape to cause gaps to be positively created between the insulating layers of the coil to permit synthetic resin to be easily filled into these gaps. Thus, synthetic resin is filled between the layers of the tape and in the gap. The number of the stringlike substances as well as the material and diameter of the string-like substance may be optimally determined of impregnation and impregnation is completed for these hours. In contrast, an electrostatic capacitance (prior art) as represented by a curve b shows that no equilibrium state is attained even for 12 hours of impregnation and the electrostatic capacitance as attained for these hours is lower than that of this invention as attained for 6 hours of impregnation. The coil manufactured according to the method of this invention was broken up and observed. The synthetic resin was found to be completely impregnated down to the most inner layer of the mica tape. With a coil so manufactured according to the conventional method, synthetic resin was impregnated sufficiently down to the 10th layer of the mica tape and insufficiently down to the 11 to 15th layers of the mica tape, and down to the 16 to 20th layers of the mica tape no synthetic resin was impregnated except for the locations 30 cm apart from each end of the mica tape. The degree to which synthetic resin is impregnated into the mica tape imparts an important influence to electric characteristics.

By way of comparison, experiments were conducted as to the electrical characteristics (tan 6, voltages and breakdown voltages) of an insulated coil as manufactured according to the conventional method. The re-' sults are shown in the following Table.

Table Applied voltage tan 8 Breakdown (KV) 3 6 ll l5 I8 20 voltage (KV/mm) A 0.39 0.40 0.41 0.43 0.45 0.58 0.75 26 to 30 B 0.45 0.55 0.81 1.53 2.31 2.75 3.l0 15 to 20 dependent upon insulation conditions, such as the viscosity of the impregnating synthetic resin, thickness of the insulation (turns of the insulating tape) etc. The impregnating synthetic resin and synthetic resin constituting the stringlike substance are, when heat-treated, fused together with the result that their respective boundaries cease to exist and a unitary structure is obtained. The synthetic resin so fused together is cured, under the action of a curing agent added therein, to form together with said mica a mechanically strong insulating layer excellent in electrical insulation. Thereafter, the coil is press-formed into an insulating coil, leaving the core of the string-like substance between the insulated layers as shown in FIG. 7. Since the core of the string-like substance is very fine in thickness, i.e., of the order of about 100 denier, no obstacle is encountered in forming an insulated coil. Furthermore, since synthetic resin is also impregnated into the core of the string substance, there is no bad influence on an electrical insulation.

An insulation coil was manufactured, by way of comparison, according to the conventional method under the same manufacturing conditions as that of this invention except for the insertion of the string-like sub stance and the length of the impregnation time. FIG. 8 shows the results obtained by measuring the variation A as shown in Table indicates an insulated coil manufactured according to this invention and B as shown in Table denotes an insulated coil manufactured according to the conventional method. As will be understood from Table, at an applied voltage 20V, tan 8 (percent) of an insulated coil according to this invention is about one fourth that of an insulated coil manufactured according to the conventional method and breakdown voltage is about 1.5 times higher than that of the insulated coil manufactured according to the conventional method.

FIG. 9 shows an insulated coil manufactured with string-like substances located in a different position. With this embodiment the string-like substance extends over the different layer of a mica tape during the winding of a mica tape around a core conductor. For example, a mica tape 21 is wound once over the entire extent of a core conductor 20 and rewound up to a position somewhat remote from the end of the core conductor to form a two-layer portion. Then, string-like substances are positioned in a manner that they extend over the two-layered portion and the remaining onelayered portion. The mica tape is again wound over the remaining one-layered portion with the string-like substance inserted therebetween, thus presenting a twolayered coil. Then, the mica tape is further wound over the entire extent of the core conductor to present a three-layered coil. Therefore, one portion of the stringlike substance is positioned between the two-layered portion and three-layered portion, and the remaining portion of the string-like substance is located between one-layered portion and two-layered portion. Likewise, the mica tape is sequentially wound with the string-like substance inserted therebetween. This permits synthetic resin to be easily filled from the outside layer into the inside layer, thus obtaining a good insulated coil at a relatively short impregnation time.

What we claim is:

l. A method for manufacturing an insulated coil, comprising the steps of winding an insulating tape layer by layer around a conductor with and inserting at least one string-like substance having an outer peripheral synthetic resin layer between the layers of the insulating tape so that a gap is created around the substance between the adjacent layers, impregnating a molten synthetic resin between the layers of the insulating tape and into said gap, and heating the resultant coil to cause the impregnated synthetic resin to be fused together with the outer peripheral synthetic resin layer of the string-like substance to provide an insulated coil.

2. A method according to claim 1 in which after the insulating tape is wound around the conductor'the resulting coil is heated at a predetermined temperature for drying while vacuum treated to cause a gap and a space between the tape layers to be evacuated.

3. A method according to claim 2 in which said heating step includes pressing the insulating tape from the outside into a shape.

4. A method according to claim 1 in which said synthetic resin impregnating step comprises dipping the conductor wound with the tape into a synthetic resin and pressing the synthetic resin.

5. A method according to claim 1 in which the stringlike substance has a core yarn made of material different from that of said outer peripheral layer of the string-like substance.

6. A method according to claim 1 in which the stringlike substance has a core yarn made of material the same as that of said outer peripheral layer.

7. A method according to claim 1 in which synthetic resin forming the outer peripheral layer of the stringlike substance is made of the same material as the impregnating synthetic resin.

8. A method according to claim 1 in which the stringlike substance is located between a first and a second layer of said tape along a first portion of said conductor and between said second layer and a third layer of said tape along a second portion of said conductor. 

1. A method for manufacturing an insulated coil, comprising the steps of winding an insulating tape layer by layer around a conductor with and inserting at least one string-like substance having an outer peripheral synthetic resin layer between the layers of the insulating tape so that a gap is created around the substance between the adjacent layers, impregnating a molten synthetic resin between the layers of the insulating tape and into said gap, and heating the resultant coil to cause the impregnated Synthetic resin to be fused together with the outer peripheral synthetic resin layer of the string-like substance to provide an insulated coil.
 2. A method according to claim 1 in which after the insulating tape is wound around the conductor the resulting coil is heated at a predetermined temperature for drying while vacuum treated to cause a gap and a space between the tape layers to be evacuated.
 3. A method according to claim 2 in which said heating step includes pressing the insulating tape from the outside into a shape.
 4. A method according to claim 1 in which said synthetic resin impregnating step comprises dipping the conductor wound with the tape into a synthetic resin and pressing the synthetic resin.
 5. A method according to claim 1 in which the string-like substance has a core yarn made of material different from that of said outer peripheral layer of the string-like substance.
 6. A method according to claim 1 in which the string-like substance has a core yarn made of material the same as that of said outer peripheral layer.
 7. A method according to claim 1 in which synthetic resin forming the outer peripheral layer of the string-like substance is made of the same material as the impregnating synthetic resin.
 8. A method according to claim 1 in which the string-like substance is located between a first and a second layer of said tape along a first portion of said conductor and between said second layer and a third layer of said tape along a second portion of said conductor. 